BOSTON — Former Republican Sen. Scott Brown has decided not to run in a June special election to fill the Massachusetts U.S. Senate seat vacated by John Kerry, local media reported on Friday, a move likely to dim Republican chances of picking up the traditionally Democratic-held seat.

The Boston Herald reported that it had received a text message from Brown reporting that the paper was “the first to know” of his plans not to seek the seat.

Kerry, a Democrat, has left the Senate to become U.S. secretary of state.

Brown stunned the liberal establishment of Massachusetts in 2010 when he won a special election to fill the seat held by the late Edward Kennedy, becoming Massachusetts’s first Republican senator in three decades.

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He left the Senate in January after he lost a re-election bid to Democrat Elizabeth Warren, a former Harvard professor.

Brown had been under pressure from local party officials to either launch a formal campaign or step aside to clear the way for an April 30 primary ahead of the June 25 special election.

So far two Democratic U.S. representatives, Edward Markey and Stephen Lynch, have declared their candidacies.

Recent polls of likely voters showed Brown with a modest lead over Markey and a stronger lead over Lynch in a theoretical election matchup.

“He has basically been campaigning nonstop for three years,” Lynch said in a statement referring to Brown. “It’s perfectly understandable that he wouldn’t want to undertake another campaign. I wish all the best to Scott and his family.”

Democrats currently hold 53 U.S. Senate seats to 45 for the Republicans. There are two independent senators.

Massachusetts Governor Deval Patrick, a Democrat, on Jan. 30 named his former chief of staff, William Cowan, to hold Kerry’s U.S. Senate seat until a successor is picked.

Cowan told reporters he viewed the appointment as temporary and had no plans to run in the special election.

Staying out of the Senate race leaves Brown the option of running for governor of Massachusetts in 2014.